The present invention relates to apparatus for bending pipes or tubes having end fittings thereon and a method for using such apparatus.
Hydraulic and pneumatic systems aboard modern day aircraft are rather complex and require pipes or tubes to be formed with high geometric precision and quality. Typically the pipe or tube systems are fabricated from an initially straight pipe or tube by sequentially bending the tube, such bending being carried out in a variety of bending planes.
It is known to carry out such complex pipe or tube bending on an automated machine having numerically controlled and integrated operational parameters such that the machine automatically moves the pipe between consecutive bends, rotates the pipe to achieve bends in different planes and automatically controls the proper bending angle. European patent 0 168 331 describes a typical automated machine having a rotating shaping roller or die with a vertical rotation axis, that is provided with a circumferential semi-circular groove into which the pipe is placed. A second jaw clamps the pipe to the shaping or bending roller as they are rotated about the vertical axis to bend the pipe. The opposite end of the pipe is mounted in a chuck of the machine which may be traversed longitudinally to advance the tube, such that it may be bent in various locations, and which may be rotated to affect bending in various planes.
While the pipe and tube systems fabricated by the use of such machines have generally proven satisfactory, generally such machines are limited as to the bending of the pipe or tube close to its end, particularly where end fittings have been attached to the pipe or tube. In tubing having diameter between 6 and 25 millimeters, it has generally been proven infeasible to bend the pipe closer to the end than a distance generally equal to 2.5 times the diameter. In those instances where the geometrical requirements of the tubing is such that this limit cannot be met, it has been necessary to perfect the bend near the end of the pipe prior to cutting it to size and attaching the end fitting. This process is not only in and of itself time consuming, but also wastes pipe or tube material and renders the inspection of the weld attaching the end fitting more difficult.
Various attempts have been made to obviate this problem as exemplified by U.S. Pat. No. 4,481,803 to Dieser and French patent 2 388 612. In Dieser, an internal mandrel is utilized in conjunction with a bending die, a clamping die and a pressure die to bend the end of the tube. The French patent describes a tube manufacturing process that includes the shaping of end segments and provides for an increase in the tube diameter.